Final answer:
In Edgar Allan Poe's story "The Cask of Amontillado", Fortunato has insulted Montresor, leading Montresor to seek revenge.
Step-by-step explanation:
In Edgar Allan Poe's story "The Cask of Amontillado", Fortunato has insulted Montresor. Montresor says, "The thousand injuries of Fortunato I had borne as best I could, but when he ventured upon insult, I vowed revenge." This quote indicates that Fortunato has done something to deeply offend and insult Montresor, which leads Montresor to seek revenge.